Low-viscosity to medium-viscosity adhesives, for example Sicomet 85, Sicomet 77, omniFit 15 M and omniFit 200 M, are used for bonding substrates with narrow to medium-sized gaps (0.01 to 0.2 mm), according to the particular requirements and the material classification. These adhesives have a Brookfield viscosity of up to about 1,000 mPas at 20.degree. C. They are eminently suitable for filling the entire gap, particularly when the parts to be bonded are fitted together before application of the adhesive and good capillary effects are required for completely wetting the entire substrate surfaces. Where relatively large gaps (0.2 to 2 mm) or spaces are to be bridged or filled, high-viscosity or thixotropicized adhesives with gap-bridging properties (for example metallon FL and Stabilit express) are used. The viscosity of metallon FL is 110,000 to 120,000 mPas for the binder and 15,000 to 30,000 for the hardener (see Henkel KGaA's technical information sheet on "Sicomet/omniFit"). In view of the high viscosity or limited capillary effects, substrates which have already been fitted together with relatively large gaps are difficult or impossible to bond by subsequent application of adhesive.
The adhesives mentioned above are unsuitable for bonding substrates which have already been fitted together both with small and with relatively large gaps or spaces in between either because of inadequate capillary effects or incomplete wetting of the substrate surfaces or through the absence of gap-bridging or space-filling properties.
Against the background or this prior art, the problem addressed by the present invention was to provide low-viscosity to medium-viscosity reactive adhesives with gap-bridging or space-filling adhesive properties.